Fig. 14.23. Temperature dependence of the thermoelectric power of
(a) K-doped C60 and (b) Rb-doped Cw. The dashed lines in (a) and
(b) are an extrapolation of the linear S(T) behavior to show the low temperature hump associated with phonon drag more clearly. In both (a) and (b) the superconducting Tc is indicated, (c) The temperature dependence of the thermopower of K, C7(l at the stoichiometry of the maximum-conductivity phase (x ~ 4). The circles and triangles are for the data from samples with room temperature electrical conductivities crRT = 575 S/cm and 10 S/cm, respectively [14.27],
For the M3C60 compounds, carriers from the three tXu LUMO-derived bands make a contribution 5,(7) to the total thermopower 5(7") in accordance with
in which 5,(7) is the contribution from carriers in each band i and cr, is the corresponding conductivity. Assuming an equal contribution from each band to 5(7), we can write for the diffusion thermopower
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